The present invention relates to a method for rewriting information written down in each of four defect management areas on an optical disk of a rewritable type, a partial ROM type, or a full ROM type according to ECMA standard, the information written down in each of the four defect management areas being substantially the same.
ANSI/X3B11/89-120 has proposed a method for managing defective sectors on a 90 mm optical disk of a rewritable type, a partial ROM type, or a full ROM type where defective sectors are arranged so that the optical disk can be made compatible with various kinds of disk storage. The ANSI standard conforms to the ECMA standard. A description will now be given of the abstract of the ECMA standard.
A data zone of a preaddressed optical disk according to the ECMA/TC31/91/32 standard comprises, as shown in FIG. 1, four defect management areas (DMA), a rewritable zone, and an embossed zone. Incidentally, the term "a data sector", as used herein, means a sector on which a user records information. The term "a spare sector", as used herein, means a spare sector for a defective sector which is discovered while an optical disk is being verified or generated while the optical disk is being used. The term "a group", as used herein, means an element which correlates the data sector with the spare sector.
Each DMA has a length of 37 sectors including all information about defective sectors and comprises a disk definition sector (DDS), a primary defect list (PDL) and a secondary defect list (SDL). The address of the first sector of the DMA 1 is given by (track 0, sector 0). The address of the first sector of the DMA 2 is given by (track 1, sector 14). The address of the first sector of the DMA 3 is given by (track 9997, sector 12). And the address of the first sector of the DMA 4 is given by (track 9998, sector 14). Incidentally, the DDS of each DMA is located at each of the above addresses. The number, corresponding to the number of predetermined defective sectors, of PDL is located subsequent to the DDS. The number, corresponding to the number of predetermined defective sectors, of SDL is located subsequent to the PDL. The term "DDS", as used herein, means a table of contents shown in FIG. 2 indicating data of defective sectors. The term "PDL", as used herein, means, as shown in FIG. 3, a list of defective sectors discovered while the optical disk is being verified or while the optical disk is being formatted. The term "SDL", as used herein, means, as shown in FIG. 4, a list of defective sectors generated while the optical disk is being used. Therefore, if a defective sector is discovered while the disk is being verified or being formatted, the DDS and PDL has to be changed. If the number of defective sectors is greater than the number of spare sectors included in the group, the DDS, PDL and SDL have to be changed. On the other hand, if a defective sector is generated while the optical disk is being used, the DDS and the SDL have to be changed. If the number of groups of the rewritable zone or the number of groups of the embossed zone is to be rewritten, only the DDS is changed. If the DDS, PDL or SDL is to be changed, each DMA instead of being partially overwritten, is rewritten as a whole. In this case, according to the conventional DMA rewriting method, the old data of the DMA 1 is first deleted by an optical head and then new data is written down thereon. The old data of the DMA 2 is deleted and then new data is written down thereon. Subsequently, the optical head is moved to the DMA 3, and the old data of the DMA 3 is deleted and then new data is written down thereon. Lastly, the old data of the DMA 4 is deleted and then new data is written down thereon. Incidentally, data concerning defective sectors to be written down in respective DMA 1 to 4 are substantially the same as each other.
However, the above conventional DMA rewriting method has the following disadvantage. That is, if the DMA is interrupted from being rewritten while the optical head is being moved from the DMA 2 to the DMA 3 because of a power failure, the defective sector data of the DMA 1 and 2 becomes different from that of the DMA 3 and 4. The optical disk consequently has some DMAs having different defective sector data.